Battery Charger dead on cordless drill.

[Jerry.Tan]

I picked up a Toolshop brand cordless drill at a garage sale. It was only $1.00 so I took a chance, and the tips and drill bits that came with it are worth a buck.

The drill is clean, and the battery appears fairly new, since it's cleaner than the drill. (Of course appearance really dont matter). The charger on the other hand is dirty and was filled with crud in the battery hole.

This charger is a 2 piece type. The stand where the battery goes, and a wall wart which plugs into the stand. However, the red LED dont light with or without the battery, so I measured it with a meter and it's not putting out any voltage. (should be 18V DC)

I know Toolshop is a Menards brand. I actually have several of their corded tools and have been very satisfied with them. Anyhow, I'm sure a replacement charger is probably costly, and since I dont know if the drill and battery work, I'm not going to spend money on it, unless I find one cheap on ebay.

But I often see Wall Warts at Goodwill and other similar stores. I'm wondering if I was to find an 18VDC one with enough amperage, if I could just plug that into the base? Anyone ever tried such a thing?

Actually I'm wondering what would happen if I hooked a 12V auto battery charger to that base. I know it wont get a full charge, but if I can just get some charge into the battery, I'll know if the drill works.

Thanks

[mike]

That's probably an uncontrolled charger. The resistance in the circuit limits the charge current. Hooking up an arbitrary charger is likely not gonna end well. You don't want to be hit when the battery explodes. There's a reason they say, "use only the charger that came with the device."

What usually happens is that one or more of the cells in the battery pack is shorted. That reduces the voltage, so the current from the transformer is way more than the design value. This overcharges the remaining cells. In the process, the transformer in the wall wart overheats and blows the thermal fuse that's embedded in the transformer. You can verify this with an ohm-meter applied to the AC input end of the wall wart.

If the battery is labeled 18V, you probably have 15 cells in series. A car battery charger probably won't do anything, but they are so uncontrolled that you never know. You really need 21V or so.

If you can't be dissuaded from trying, at least put a light bulb in series so you don't blow yourself up. A 120V 60W incandescent light bulb will limit the current to somewhere around 0.2 amps, but you still need a voltage source of more than 18VDC. And you need safety glasses. Yes, they do explode.

You can test your drill with whatever 12V battery you have around...being careful not to short the wires and blow that up. It won't go fast, but it should run.

The likely scenario is that your battery is unusable as is your charger.

FWIW, I have never purchased a used working drill with a usable battery...that's why they're for sale, it costs more for a battery than a new drill. If they broke the drill, sometimes the battery is ok. So I have a box full of mismatched drills and batteries.

Bottom line...if you don't know what you're doing, trash it. The question suggests that's the case. It's not as simple as it sounds. It's a shame to ruin a perfectly good set of safety glasses.

[David L. Martel]

Jerry,

Does the wall wart work? What is it supposed to supply? How much time and money do you want to spend on this project.?

Dave M.

[philo]

You can pick up a cheap replacement if you want.

The voltage should be approx the same as the old one (it can be slightly higher) and be sure to make sure the polarity is correct.

The current rating of the replacement should be equal to or greater than that of the old one

[sms]

A lot of the power tools still use NiCad batteries which can be fixed when they develop a short. You need to zap the individual cell with a high current from a large capacitor, or a high current DC power supply. Doesn't work for NiMH or Li-Ion.

[hrhofmann]

You should measure for output from the wall-wart before doing anything else . For a 12V power pack, the no-load output from the wall-wart could be any where from 12 - 18V AC. It is possible that the rectifier diodes are also i n the wall-wart. In that case, you should see about 15V DC. The label on the case of the wall-wart might indicate what the output voltage should be.

To measure the voltage, use pins to break thru the insulation on the wires from the wall-wart to the battery stand, and connect the voltmeter to the p ins. Insert each pin far enough away from the other pin so that they canno t accidently touch each other (learned that the hard way many years ago(gri n)).

Let us know what you find out, and then we can give further advice, such as what to do about shorted NICAD cells, as another poster has mentioned, man y of those short failures can be repaired .

[Tony Hwang]

First thing first, is the wall wart output DC or AC? Can you take apart the charging base and look see what kinda circuit is in there? What type battery is it?

[mike]

From the tone of a posting, you can often infer the level of experience and equipment available to the poster. I try to present input in a language and level of detail appropriate for the situation. Based on the question, I'd bet that the OP doesn't have the stuff required for safe dendrite blasting.

FWIW, I've never had much luck blasting a battery. I have had some limited success blasting individual cells. A dendrite is a short. When you blast it out, you make the hole in the separator even bigger. Self discharge makes the pack useless unless you charge it and use it immediately. And the short returns eventually. If you're not paying close attention, you can ruin the new wall wart too.

I've tried replacing individual cells from another bad pack. Never had much luck with that either. If the packs are abused and shorting, it's just a matter of when the next domino will fall.

[gregz]

Op says measured something. Where ? If the wall wart says 18vdc, could be pulsating dc average. It's not a given. I would measure the battery first. Too low of a voltage might indicate failure of cells or entire pack. Is the battery voltage labeled ?

Greg

[Art Todesco]

First of all, repairing a charger is pretty difficult, especially without a schematic. When I lived in a Menards area, I bought a universal drill charger for not too much $$$. I had an old Skil 12v drill, which was one of the voltages/battery types listed. It worked very well, but didn't really fit the Skil battery. A little Moto-tooling and it then fit and charged perfectly. It probably would have worked with clip lead also. As I haven't lived in a Menards area for some number of years, I don't know if they still have anything like that.

[Dana F Bonnett]

The charger for my Makite 9.6v drill stopped charging. Opened it up and found a blown fuse inside. Got a new one at a local electronics parts store and that was the fix. FWIW YMMV